Does Occluded Render require Unity Pro?
No; Occluded Render works with Unity Indie and Pro.
Does Occluded Render work in Differed/Forward/Vertext Lighting mode?
Yes Occluded Render supports all lighting modes with the exception of Rim which does not support Vertext Lighting.
Wireframe doesn't work ... why?
Wireframe uses geometry shaders to render an accurate effect however this is currently only support by DirectX ... in Unity.
We are looking at other methods for Wireframe to complement the DX implementation though these new shaders do not have a release date as of yet.